Infection with hepatitis B virus in man is a major public health problem of world-wide concern. Its involvement in chronic liver disease or cancer of the liver among the carriers signifies the importance of investigating the basic biology of this virus, which is crucial to the development of safe and practical procedures for control of HBV infection. The general aim of the proposed project is to begin to understand the genetic structure of HBV, to assess the entire coding capacity of viral genome and to examine the role of HBV in hepatocellular carcinoma. HBV-like viruses recently found associated with animals (ground squirrel, woodchuck and ducks) offer opportunities to study certain aspects of the project heretofore not possible with humans. As an initial step in this study, I intend to prepare a functional map of the HBV genome. Success in transfection of mammalian cells with cloned HBV DNA significantly overcomes the limitations imposed by the lack of a tissue culture system for HBV. Using eukaryotic vectors, in which genomic and subgenomic portions of HBV DNA can be inserted and subsequently introduced into mammalian cells, we hope to define sequences which determine viral gene expression. emphasis will also be placed on attempts to establish a cell line that will contiually produce viral proteins and be capable to propagating viral particles. Finally, we will clone in a bacteriophage Gamma vextor integrated HBV sequences from tumorous and nontumorous liver DNAs. The integrated state of HBV DNA will in each case be investigated by determining the organization of cloned segments by restriction endonuclease analysis. This investigation is expected to shed light on the significance of the integrated HBV sequences present in tumorous tissue. We then propose to use the cloned integrated forms of HBV DNAs with their adjacent cellular sequences to transfect various cell lines. This investigation is expected to identify HBV sequences, if any, involved in eliciting cellular transformation.